This invention relates generally to dishwashers, and, more particularly, to dishwasher system fluid circulation assemblies.
Known dishwasher systems include a main pump assembly and a drain pump assembly for circulating and draining wash fluid within a wash chamber located in a cabinet housing. The main pump assembly feeds washing fluid to various spray arm assemblies for generating washing sprays or jets on dishwasher items loaded into one or more dishwasher racks disposed in the wash chamber. Fluid sprayed onto the dishwasher items is collected in a sump located in a lower portion of the wash chamber, and water entering the sump is filtered through one or more coarse filters to remove soil and sediment from the washing fluid. At least some dishwasher systems further include a fine filter system in flow communication with the main pump assembly to remove soil and sediment of a smaller size than those filtered by the coarse filters. The main pump assembly draws wash fluid from the sump to recirculate in the wash chamber, and the coarse and fine filters are used to continuously filter the water in the sump during the re-circulation process.
In at least some known fine filter drain systems, wash fluid is pumped from the fine filter directly into the fine filter system. As sediment builds up in the fine filter, pressure increases in the fine filter system, reducing the effectiveness of the filter. Thus, periodically, it is necessary to drain the fine filter system to reduce pressure in the fine filter system and to remove the accumulated soil and sediment. Efficient removal of soil and sediment, however, is problematic in known fine filter systems.
In an exemplary embodiment, a fluid circulation assembly is provided including a main pump, a spray arm conduit, a fine filter assembly, a drain pump, and a sump. The main pump includes a pump inlet and a discharge in flow communication with the spray arm conduit. The fine filter assembly includes a fluid inlet in flow communication with the spray arm conduit and a drain tube. The drain pump is in flow communication with the drain tube; and a sump is in flow communication with the main pump and the drain pump.
The fine filter assembly is efficiently cleaned by operating the fluid circulation assembly as follows. The main pump is activated to pump wash fluid in the fine filter assembly, and the drain pump is activated to drain the fine filter assembly while the main pump remains activated. Both the main pump and the drain pump are then operated for a selected time period, thereby maintaining an inlet flow into the fine filter assembly while simultaneously creating a drain suction at the fine filter assembly drain tube to flush the fine filter assembly. The main pump is then deactivated and the drain pump is operated to drain remaining fluid in the fluid circulation assembly.
Indirect feeding of the fine filter assembly through the spray arm conduit, rather than directly from the main pump, reduces operating pressure in the fine filter assembly, thereby enhancing fine filter performance and facilitating a use of the drain pump inlet as a soil collection chamber. In addition, the lower spray arm includes downwardly directed discharge ports that backflush the fine filter assembly as the filter is flushed and sweep soil accumulated in the fine filter assembly toward the fine filter drain tube. Thus, by operating the main pump to provide backflushing water jets and maintain an inlet flow to the fine filter assembly, and further by operating the drain pump concurrently with the drain pump the provide a suction at the fine filter assembly drain tube, soil in the fine filter assembly is quickly and efficiently removed.